Engine - Hesitation, OBD Fault 17/DTC P0121 Set
17/11/9519/02/95/US
SUBJECT
Throttle Adjustment Screw
MODEL
Range Rover 4.0/4.6
Range Rover Classic
Discovery
Defender
AFFECTED VEHICLES
LP 318013 Onward
LH 662245 Onward
LJ 166956 / 502785 Onward
LD 970607 Onward
DETAIL
If a customer complains of initial drive away hesitation or of an OBD fault 17 on a 14CUX ECM equipped car or drive away hesitation and/or a PO121 fault on a GEMS equipped car the problem may be caused by the throttle adjusting screw. On vehicles built prior to the VIN range above movement of the throttle stop screw from its original factory set position could cause the problems above. If this occurs the throttle plate may sweep over center.
As from above VIN range the throttle adjusting screw has been securely set at the factory and must not be adjusted. The setting screw has been locked into position and any attempt to move it may result in damage to the screw.
ACTION REQUIRED
Information only: On vehicles which display the symptoms described above, follow the procedure below.
PARTS INFORMATION
Loctite 242 - source locally
PROCEDURE
1) Remove the hose from the mouth of the plenum chamber.
2) Operate the throttle and observe the throttle disc to determine if it is travelling over center when it closes. You may find it easier to measure the depth to the top and bottom of the disc to determine whether or not it is over center in the closed position.
3) The throttle disc should be in the vertical position +/-.O.005". If it is not, the plenum chamber will need to be removed to access the throttle adjustment screw. See section 19 "Fuel System, Plenum Chamber" of Workshop Manual.
4) With the plenum removed, unscrew the throttle stop screw as shown in illustration and remove, with a 3/32" Allen key.
WARRANTY
Normal warranty policy and procedures apply
COMP. CODE
2W4W
SRO
19.20.89/26 - Check throttle disc adjustment -
0.25 hr
19.20.89/27 - Check and adjust throttle disc - 1.35 hrs
5) Clean the set screw and the hole it fits in.
6) Refit the set screw from the underside of the plenum. When the screw nears the top of the hole apply Loctite 242 into the threaded hole and wind the screw into the position required to set the throttle disc vertical in the plenum bore (+/-.O.005").
7) Refit the plenum to the engine.
8) On GEMS Equipped Cars
Using TestBook, check that the actual closed throttle position voltage is less than the stored closed throttle voltage when the throttle disc is shut. Observe via "Subsystem Test" selection and then the "ECM Option" icons. If the closed throttle voltage is greater than the stored closed throttle voltage, reset using TestBook. Both values should be in the 0.60 V - 0.85 V range. If these voltages are not set accurately the Idle speed control system may not function correctly/idle correctly and/or the vehicle may intermittently stall.
On 14CUX Equipped Cars
The throttle close position should be between 0.30 V - 0.40 V.
9) Test drive vehicle.